as we discussed few hours ago, you may use the postread control to
capture the DN of an entry that's just been added, since the "X-ORDERED
'SIBLINGS'" will add a leading {<digits>} to the distinguished value.
I've just committed a couple of fixes to HEAD that allow to
1) use the control (the absence of o_bd was causing access control to
fail in the internal search that looks up the freshly added data)
2) use "1.1" as requested attribute to just lookup the DN, if you're
fine with that; to make things more general, you might want to require
the entryDN instead.

The example code that adds the postread control and parses the result is
in clients/tools/common.c. Maybe it could be worth having a pair of
library calls much like we have for pagedResults:
ldap_create_page_control() and ldap_parse_page_control() (and their
building blocks) so that they can simply be called from within the
python wrapper.